多线程编程(19) - 不使用同步工具, 手动协调线程依次执行

在前面例子的基础上, 探讨新问题.

假如我们想让几个线程(例子中是 3 个)依次执行, 我们可以使用临界区、信号、互斥等手段;
但下面第一个例子什么同步工具都没用, 也达到了目的; 方法是: 让前一个线程在结束前顺便启动下一个线程.

第二个例子使用了互斥对象配合 WaitForSingleObject 函数, 也达到相似的目的.

---

效果图(两个例子的效果图差不多, 但第二个例子的执行顺序不好保证):

---

第一个例子的代码文件:

---

unit Unit1;interfaceuses  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,  Dialogs, StdCtrls, ExtCtrls;type  TForm1 = class(TForm)    PaintBox1: TPaintBox;    PaintBox2: TPaintBox;    PaintBox3: TPaintBox;    Button1: TButton;    procedure Button1Click(Sender: TObject);    procedure FormDestroy(Sender: TObject);  end;var  Form1: TForm1;implementation{$R *.dfm}const  colors: array[0..2] of TColor = (clRed, clGreen, clBlue);var  hArr: array[0..2] of THandle;  panitArr: array[0..2] of TPaintBox;function ThreadFun(p: Pointer): Integer; stdcall;var  i,n,x1,y1,x2,y2: Integer;  ThreadID: DWORD;begin  n := Integer(p);  panitArr[n].Color := colors[n];  for i := 0 to 50 do with panitArr[n] do  begin    x1 := Random(Width); y1 := Random(Height);    x2 := Random(Width); y2 := Random(Height);    Canvas.Lock;    Canvas.Ellipse(x1,y1,x2,y2);    Canvas.Unlock;    Sleep(2);  end;  {在前一个线程收尾时, 如果新建线程不超过 3 个就继续建立}  Inc(n);  if n < 3 then hArr[n] := CreateThread(nil, 0, @ThreadFun, Ptr(n), 0, ThreadID);  Result := 0;end;procedure TForm1.Button1Click(Sender: TObject);var  ID: DWORD;begin  panitArr[0] := PaintBox1;  panitArr[1] := PaintBox2;  panitArr[2] := PaintBox3;  {开始只建立了一个线程, 并传入 0 参数作为标识}  hArr[0] := CreateThread(nil, 0, @ThreadFun, Ptr(0), 0, ID);end;procedure TForm1.FormDestroy(Sender: TObject);var  i: Integer;begin  for i := 0 to Length(hArr) - 1 do CloseHandle(hArr[i]);end;end.

窗体文件:

---

object Form1: TForm1  Left = 0  Top = 0  Caption = 'Form1'  ClientHeight = 156  ClientWidth = 321  Color = clBtnFace  Font.Charset = DEFAULT_CHARSET  Font.Color = clWindowText  Font.Height = -11  Font.Name = 'Tahoma'  Font.Style = []  OldCreateOrder = False  OnDestroy = FormDestroy  PixelsPerInch = 96  TextHeight = 13  object PaintBox1: TPaintBox    Left = 8    Top = 8    Width = 97    Height = 113  end  object PaintBox2: TPaintBox    Left = 111    Top = 8    Width = 98    Height = 113  end  object PaintBox3: TPaintBox    Left = 215    Top = 8    Width = 98    Height = 113  end  object Button1: TButton    Left = 238    Top = 126    Width = 75    Height = 25    Caption = 'Button1'    TabOrder = 0    OnClick = Button1Click  endend

第一个例子的代码文件(窗体同上):

---

unit Unit1;interfaceuses  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,  Dialogs, StdCtrls, ExtCtrls;type  TForm1 = class(TForm)    PaintBox1: TPaintBox;    PaintBox2: TPaintBox;    PaintBox3: TPaintBox;    Button1: TButton;    procedure Button1Click(Sender: TObject);    procedure FormDestroy(Sender: TObject);  end;var  Form1: TForm1;implementation{$R *.dfm}const  colors: array[0..2] of TColor = (clRed, clGreen, clBlue);var  hArr: array[0..2] of THandle;  panitArr: array[0..2] of TPaintBox;  hMutex: THandle; {互斥对象的句柄}function ThreadFun(p: Pointer): Integer; stdcall;var  i,n,x1,y1,x2,y2: Integer;begin  n := Integer(p);  panitArr[n].Color := colors[n];  if WaitForSingleObject(hMutex, INFINITE) = WAIT_OBJECT_0 then  begin    for i := 0 to 50 do with panitArr[n] do    begin      x1 := Random(Width); y1 := Random(Height);      x2 := Random(Width); y2 := Random(Height);      Canvas.Lock;      Canvas.Ellipse(x1,y1,x2,y2);      Canvas.Unlock;      Sleep(10);    end;    ReleaseMutex(hMutex);  end;  Result := 0;end;procedure TForm1.Button1Click(Sender: TObject);var  ID: DWORD;  i: Integer;begin  panitArr[0] := PaintBox1;  panitArr[1] := PaintBox2;  panitArr[2] := PaintBox3;  CloseHandle(hMutex);  hMutex := CreateMutex(nil, False, nil);  for i := 0 to Length(hArr) - 1 do    hArr[i] := CreateThread(nil, 0, @ThreadFun, Ptr(i), 0, ID);end;procedure TForm1.FormDestroy(Sender: TObject);var  i: Integer;begin  CloseHandle(hMutex);  for i := 0 to Length(hArr) - 1 do CloseHandle(hArr[i]);end;end.

转帖：http://www.cnblogs.com/del/archive/2009/02/19/1394413.html